Complete Fluid Specifications: 2015 GMC Sierra 1500

As an ASE-certified master technician, I’ve seen countless 2015 GMC Sierra 1500s roll through my bay. Whether you're hauling, towing, or just commuting, keeping this truck's fluids fresh and perfectly matched to General Motors factory specifications is the single best way to ensure longevity.

The 2015 model year (part of the K2XX generation) came with three stellar EcoTec3 gas engines: the 4.3L V6, 5.3L V8, and 6.2L V8. Below is your comprehensive guide to every factory-specified fluid, capacity, and service pitfall for the 2015 GMC Sierra 1500.

Quick reference

Fluid	Type/Spec	Capacity
Engine Oil (4.3L V6)	5W-30 GM dexos1 Gen3 (API SP)	6.0 qts (5.7 L) with filter
Engine Oil (5.3L / 6.2L V8)	0W-20 GM dexos1 Gen3 (API SP)	8.0 qts (7.6 L) with filter
Engine Coolant	DEX-COOL 50/50 Premix (GM 6277M)	16.3 – 17.6 qts (verify in manual)
Transmission (6-Speed)	DEXRON-VI ATF	Pan drop: ~6.0 qts
Transmission (8-Speed)	DEXRON HP (Mobil 1 LV ATF HP)	Pan drop: ~7.4 qts
Transfer Case (4WD)	DEXRON-VI ATF	1.6 qts (1.5 L)
Front Differential	75W-90 Synthetic Gear Lube	1.6 qts (1.5 L)
Rear Differential	75W-90 Synthetic Gear Lube	2.7 - 2.8 qts (2.6 L)
Brake Fluid	DOT 3 (Delco Supreme 11)	Flush until clear
Power Steering	N/A (Electric Power Steering)	N/A
Washer Fluid	Standard Washer Solvent	Fill to line

(Note: The 2015 GMC Sierra 1500 was only available with gasoline engines, so Diesel Exhaust Fluid / DEF is not applicable. Always verify capacities in your owner's manual or OEM service info.)

Engine Oil

General Motors has stringent requirements for their EcoTec3 engines. For the 4.3L V6, you need a 5W-30 viscosity. For the 5.3L and 6.2L V8s, GM mandates a 0W-20 viscosity.

Regardless of engine size, you absolutely must use an oil carrying the GM dexos1 Gen3 license (which supersedes the older Gen1 and Gen2 specs) and API SP certification. The dexos1 Gen3 specification provides superior protection against Low-Speed Pre-Ignition (LSPI), which is critical for modern direct-injected engines.

• Interval: Follow the Oil Life Monitor (OLM), but as a master tech, I recommend never exceeding 5,000 to 7,500 miles, especially if you tow or idle frequently.
• Pitfall: Using cheap, non-dexos oil can cause excessive wear on the variable valve timing (VVT) actuators and Active Fuel Management (AFM) lifters, leading to a catastrophic valvetrain failure.

Engine Coolant

The Sierra uses DEX-COOL (GM spec 6277M). This is an Organic Acid Technology (OAT) coolant, recognizable by its distinct orange color.

• Interval: Factory recommendation is 150,000 miles or 5 years, whichever comes first. I recommend doing a drain and fill every 5 years regardless of mileage.
• Pitfall: Never mix DEX-COOL with green conventional coolant or HOAT coolants. Mixing coolant types creates a muddy, sludgy gel that will clog your heater core and ruin your water pump. Always use distilled water if you are mixing concentrated DEX-COOL, or simply buy the 50/50 premix.

Transmission Fluid

Your Sierra will have either the 6L80 6-speed or the 8L90 8-speed automatic transmission. Fluid specs differ significantly:

• 6-Speed (6L80): Uses standard DEXRON-VI.
• 8-Speed (8L90): Uses DEXRON HP (specifically Mobil 1 Synthetic LV ATF HP, GM part number 19417577).
• Interval: Under severe duty (towing, city driving), drop the pan and change the filter/fluid every 45,000 miles.
• Pitfall: The 8L90 transmission is notorious for torque converter shudder. GM released a Technical Service Bulletin (TSB) mandating a fluid flush to the updated Mobil 1 LV ATF HP (blue label) to resolve this. Do not use generic "multi-vehicle" ATF in these advanced gearboxes.

Transfer Case (4WD Models)

If your truck is equipped with four-wheel drive, the transfer case (typically an Magna Powertrain unit) requires DEXRON-VI automatic transmission fluid.

• Interval: Replace every 45,000 miles for severe service.
• Pitfall: Do not use gear oil or older Auto-Trak II fluid in this transfer case. Using the wrong fluid will destroy the internal clutch packs.

Differential Fluid (Front and Rear)

Both the front and rear differentials require 75W-90 Synthetic Gear Lube.

• Interval: Check level every oil change. Replace every 45,000 miles under heavy towing conditions.
• Pitfall: Most 2015 Sierras are equipped with the Eaton G80 automatic locking rear differential. Do not add friction modifiers or limited-slip (LSD) additives. The G80 locker is designed to operate on pure synthetic 75W-90; additives will prevent the centrifugal flyweight mechanism from locking properly.

Brake Fluid

GM specifies DOT 3 hydraulic brake fluid (specifically Delco Supreme 11 or equivalent).

• Interval: Brake fluid is hygroscopic (it absorbs moisture from the air). Flush the system every 2 to 3 years to prevent internal corrosion of the ABS module and brake calipers.
• Pitfall: Do not use DOT 5 (silicone-based) fluid, as it will destroy the seals in a DOT 3/4 system.

Power Steering Fluid

The 2015 GMC Sierra 1500 utilizes Electric Power Steering (EPS). There is no hydraulic power steering pump, no hoses, and no fluid to check or leak.

Washer Fluid

Use a high-quality windshield washer solvent (like Optikleen). If you live in a cold climate, ensure the fluid is rated for sub-zero temperatures to prevent the washer reservoir and pump from freezing and cracking.

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